Evolution of nuclear shape in the light Radon isotopes

Andrew Robinson, David Jenkins, Stewart Martin-Haugh University of York

Jarno Van De WalleCERN

Panu RahkilaUniversity of Jyvaskyla

Andrei Andreyev, Nick Bree IKS K.U. Leuven

Peter Butler, Tuomas Grahn, Janne Pakarin, Andrew Petts, Marcus ScheckUniversity of Liverpool

Douglas Dijulio, Andreas Ekstrom Lund Univesity

Alick Deacon, Sean FreemanUniversity of Manchester

Micheal Hass, Vivek Kumar, Kuljeet SinghWeizmann Institute of Science

Baharak Hadinia, Riccardo Orlandi, John SmithUniversity of the West of ScotlandThe Miniball Collaboration

Andrew Robinson – ISOLDE Workshop: 18th November 2008

Shape Coexistence

Atomic nucleus minimises its energy by adopting different deformed mean-field shapes.

A. Andreyev et al., Nature 405, 430 (2000)

Light Pb isotopes

Andrew Robinson – ISOLDE Workshop: 18th November 2008

Coulomb Excitation (Coulex)

d

€

d >1.25(Ap1/ 3 + AT

1/ 3) + 5 [fm]

Andrew Robinson – ISOLDE Workshop: 18th November 2008

Excitation of both Projectile and Target particle

• Probe collectivity in nucleus.

• Extraction of electromagnetic matrix elements – B(E2).

• Sensitive to the sign of spectroscopic quadrupole

moment.

• Multi-step excitations.

• Preferentially excites states which are strongly coupled to the

ground state.

Coulex with radioactive beams

Andrew Robinson – ISOLDE Workshop: 18th November 2008

70Se at REX-ISOLDEA.M. Hurst et al., PRL 98, 072501 (2007)

Coulex with radioactive beams is a highly successful method for establishing the evolution of nuclear shape

74,76Kr at SPIRALE. Clement et al., PRC 75, 054313 (2007)

Mercury Isotopes

Andrew Robinson – ISOLDE Workshop: 18th November 2008

IS425Andrew Petts – Next Talk !

Light Polonium Isotopes

Andrew Robinson – ISOLDE Workshop: 18th November 2008

Radon Isotopes

Polonium

RadonMacroscopic-microscopic models predict that deformed ground states exist beyond 202Rn.

E(4+)/E(2+) ratio for 198,200,202Rn typical of ananharmonic vibrational system.S.J. Freeman et al., PRC 50 R1754 (1994)R.B.E. Taylor et al., PRC 54, 2926 (1996); PRC 59, 673 (1999)

Evidence found for deformed intruder states in 202,204Rn which coexist with spherical ground state.D.J. Dobson et al., PRC 66 064321 (2002)

Andrew Robinson – ISOLDE Workshop: 18th November 2008

Low Lying Levels in Rn Isotopes

Andrew Robinson – ISOLDE Workshop: 18th November 2008

Radon Production

Andrew Robinson – ISOLDE Workshop: 18th November 2008

Noble gas – easily purified usingPlasma cooled transfer line.

PS Booster and ThC target:202Rn - 9 x 105 ions/C204Rn - 2 x 107 ions/C

Intensity at Miniball:202Rn – 3 x 104 ions / s204Rn – 2 x 105 ions / s

Energy Hours204Rn 2.9 MeV / u 69202Rn 2.9 MeV / u 16202Rn 2.28 MeV / u 26

x8 Miniball clusters

120Sn2 mgcm-2

202,204Rn from REX-ISOLDE

CD detector(16o-53o)

Experimental Technique

Andrew Robinson – ISOLDE Workshop: 18th November 2008

Preliminary Results: 204Rn

Andrew Robinson – ISOLDE Workshop: 18th November 2008

109Ag 3/2- 1/2-

109Ag 5/2- 1/2-

204Rn 2+ 0+

204Rn + 109Ag2.9 MeV / u

543

589

Preliminary Results: 204Rn

Andrew Robinson – ISOLDE Workshop: 18th November 2008

109Ag 3/2- 1/2-

109Ag 5/2- 1/2-

204Rn 2+ 0+

non Doppler corrected γ spectrum

Doppler correctedIS425: 184Hg Coulex

Preliminary Results: 204Rn

Andrew Robinson – ISOLDE Workshop: 18th November 2008

204Rn 2+ 0+

204Rn + 120Sn2.9 MeV / u

543

589

Preliminary Results: 202Rn

Andrew Robinson – ISOLDE Workshop: 18th November 2008

202Rn 2+ 0+

202Rn + 109Ag2.9 MeV / u109Ag 3/2- 1/2-

109Ag 5/2- 1/2-

504

525569

New Sorting Routine

• med file g ROOT tree

• General purpose sorting routine, easilyadapted to variety of experiments.

• Quick g allow analysis of data during run.(Possibility to adapt for true online sort)

• Will be made available to Miniball users

Summary

Andrew Robinson – ISOLDE Workshop: 18th November 2008

• Successfully post-accelerated 204Rn and 202Rn – heaviest radioactive beam.

• Observed Coulex of 204Rn & 202Rn.

• Good data on 204Rn - extend work to 202Rn Summer 2009

Recoil Distance Method (RDM) measurements with plunger to obtain independent lifetimes.

Conversion electron studies, help to determine properties of excited 0+ states and E0 content of j j transitions, related to rms charge radius.

Analysis is ongoing